Electronic scanning radars of the prior art consist of directional antennas produced on the basis of radiating elements, or radiating cells, assembled within an array. Modification of the amplitude and of the phase of each of the radiating elements of the array makes it possible to steer the direction of the radar beam.
The frequencies of interest for aerial monitoring applications are the S band, used for the primary radar, and in particular the sub-band from 2.9 GHz to 3.3 GHz, as well as frequency bands of a few MHz or tens of MHz situated around the frequencies 1.03 GHz and 1.09 GHz, and used for IFF applications. Current radar equipment, whether they be ground-based radars or radars onboard a carrier such as for example a vehicle, a ship or an aeroplane, generally comprise two independent systems: a rotating directional antenna dedicated to IFF applications and an array of radiating cells for the S Band radar. The rotating antenna is positioned above or alongside the S band radar antenna. The two volumes are therefore added, and this may pose a problem when transporting or installing the antennas.
The technical problem posed therefore consists in implementing, within a single radiating aperture, two distinct radiating arrays operating in different frequency bands, in particular the S band and the band dedicated to IFF applications. The arrays must each have distinct feed points enabling each of its radiating elements to be controlled independently in phase (and optionally in amplitude), and thus enabling each of the radar beams to be pointed independently.
Solutions, detailed subsequently, such as those represented in FIGS. 1a and 1b, making it possible to produce a dual-band radiating array, are known from the prior art. These solutions consist in inserting, into a mesh designed for the elements dedicated to the highest frequency band, elements dedicated to the lowest frequency band according to a mesh specific to these frequencies, either by disposing them at regular intervals between the elements of the high mesh (FIG. 1a), or by overlaying them on these elements (FIG. 1b).
Though these solutions address the problem of the footprint of the array, they are not optimal in terms of performance. Indeed, the radiating elements of the array at the high frequency do not all evolve in the same environment, some being more disturbed than others by the presence of the elements of the array at the low frequency, thereby generating non-regular disturbances prejudicial to the proper operation of the radar.
The invention addresses the problem posed by describing an active antenna panel whose radiating face comprises dual-band radiating cells, disposed according to a mesh specific to the highest frequency band. The radiating elements specific to each frequency band of which these cells are composed then all operate in the same environment, thus avoiding disturbances related to heterogeneous interference on the elements of the array. There is then an excess of cell radiating elements associated with the lowest frequency band. To prevent this excess from giving rise to additional cost in respect of the radio modules required for signal transmission and reception, the antenna panel comprises a second layer in which an array of combiners is implemented. The pathways associated with the low frequency are grouped into packets by the combiners, so as to recreate a mesh close to the mesh adapted to the low frequency band. These combiners also make it possible to limit the number of feeds to the low-band hardware components, in such a way that the interface with the existing transmission and reception modules of the radar does not require any adaptations.